Power studies when a threshold is used to dichotomize a continuous trait

在对高血压或肥胖等特征的研究中，当使用任意的循环来将连续变量二分法来确定情感状态时，可能会丢失信息。使用计算机模拟评估了这种信息损失对与模型无关的连锁和关联测试的能力的影响。基因计量分析模拟程序(G.A.S.P.)被用来模拟一个连续变量，阈值设置为大约5%的人口将受到影响。100个核心家庭，每个家庭有四个孩子，这样每个家庭至少有两个孩子。考虑的模型包括：遗传力从0到0.8，完全和无连锁不平衡，以及重组比例从0到10 cM。对离散性状的Haseman-Elston(H-E)同胞对检验和TDT检验的四种变种与连续性状的H-E检验的功效进行了比较。对一致影响对的H-E检验与对连续性状的H-E检验的威力几乎相同。当存在完全连锁不平衡时，对连续性状的TDT检验比H-E检验更有效；其他检验的效力仅略好于I类错误率--G.A.S.P.、基因计量学、连锁分析、离散、连续、定量、计算机模拟

In studies of traits like hypertension or obesity, information can be lost when arbitary cirteria are used to dichotomize a continous variable to determine ?affection status.? The effect of this loss of information on the power of model-independent tests of linkage and association was evaluated using computer simulation. The Genometric Analysis Simulation Program (G.A.S.P.) was used to simulate a continuous variable with a threshold set to that approximately 5% of the population would be affected. One hundred nuclear families, each with four offspring, were acertained so that at least two offspring were afected in each family. Models considered include: heritabilities from 0 to 0.8, complete and no linkage disequilibrium, and recombination fractions from 0 to 10 cM. The power of four variations of the Haseman-Elston (H-E) sib-pair test for discrete traits and the TDT test were compared to the H-E test for a continous trait. The power of the H-E testfor concordantly affected pairs (only) was nearly identical to that of the H-E test for the continuous trait. The TDT test of association was more powerful than the H-E test for continuous traits when there was complete linkage disequilibrium; other the power of this test was only marginally better than the type I error rate - G.A.S.P., genometrics, linkage analysis, discrete, continuous, quantitative, computer simulation